In storage cabinets, which have sliding pull out components, such as shelves or drawers, it is a standard practice to employ interlocking mechanism which permits only one shelf at a time to be pulled out to prevent the cabinet from tipping over should more than one drawer or shelf be withdrawn. Because of their functional similarity with respect to this invention, drawers and pull out shelves will be referred to interchangeably and generically as pull-out components.
It will be appreciated that while this invention is illustrated as embodied in an interlock mechanism to permit only one shelf at a time to be withdrawn, the principles and features may be employed in ganglock mechanism where all pull out components are simultaneously locked and prevented from being pulled out.
One such interlocking mechanism is disclosed in U.S. Pat. No. 3,404,929 which issued in 1968 to David M. Wright et al. The mechanism employs a vertically, slidable locking bar that bridges a number of shelves or drawers and which cooperates with cam mechanism on each component to prevent them from being withdrawn after one component has been withdrawn. Each component has an identical cam assembly secured to it and the locking bar has one locking pin fixed to it for each cam, and hence, each component. The cam assembly of each component is positioned to engage one pin when the component is pulled out. The cam, in engaging the pin, urges it and the locking bar, upwardly to locate the remaining pins in positions where they block the removal of the remaining components. The locking bar and the pins fixed to it, remain in the upward or locking position until the original component is returned to its closed position. At this time, the cam associated with the returned drawer permits its associated pin and thus the locking bar to move downwardly, thus, positioning all of the pins relative to their respective cams in positions where any other component may be withdrawn from or slid out of the cabinet. This mechanism proved to be quite successful commercially.
Subsequently, U.S. Pat. No. 3,866,993 issued in 1975 to Carl J. Dean et al. which was an improvement on the above-identified Wright et al. patent. It had been determined that there was a need for storage cabinets having either different height drawers or drawers which were interchangeable. To accomplish this, it was necessary that a custom made interlock mechanism be provided for each different combination of pull-out component, for example, a combination of deep drawers at the bottom, pull-out shelves, smaller drawers above it, etc. It was also determined that many users, having different requirements, from time to time rearranged and interchanged their pull-out components. An interlock system designed for an original arrangement of components had to be discarded when the pull-out components were rearranged. The '993 patent also disclosed an interlock mechanism which had a vertically movable locking bar positioned along one side of a storage cabinet which bridged a plurality of pull-out components with cam mechanism positioned on each of the components and a locking pin subassembly associated with each cam.
However, in the '993 patent, the locking pins were adjustable heightwise along the locking bar to permit them to be located to cooperate not only with cams that were positioned at different locations as, for example, on pull-out components that differed in height, but also permitted the locking pins to be repositioned if one pull-out component was replaced with another one that differed in height.
Whereas, the adjustable feature of the '993 patent proved to be more versatile than the nonadjustable interlock mechanism of the '929 patent, the mechanism for permitting heightwise adjustability of the locking pins, after repeated usage occasionally loosened and the pins became misaligned with their associated cams. Also, after repeated usage, the locking pin positioning mechanism tended to loose its holding power and required replacement.
It is accordingly an object of this invention to provide an adjustable locking pin subassembly employed in storage cabinets having pull-out storage components, which has greater holding power than heretofore and which is less susceptible to wear after lengthy periods of usage.